Dr. Jeff Masters' WunderBlog

Are Category 4 and 5 hurricane increasing globally? (Part II)

By: JeffMasters, 14:04 GMT le 31 Mars 2006

In my blog for Monday, I opened the discussion of whether Category 4 and 5 hurricanes were increasing in number globally. Here's Part II of that discussion:

Northwest Pacific typhoon intensities questioned
The question of the integrity of the typhoon intensity data in the Northwest Pacific is critical, since this ocean basin accounts for fully 46% of the global Category 4 and 5 hurricanes since 1970. Dr. Gray and Dr. Knaff both question typhoon intensities measured by reconnaissance aircraft in the Northwest Pacific during the 1973-1986 period. The technique used to determine typhoon intensities during this period (the "Atkinson-Holliday" or AH technique), is thought to have significantly underestimated the maximum winds. Looking at a plot of all Category 4 and 5 activity since 1945 in the Northwest Pacific (Figure 6), one can that intense typhoons were about as common in the 1950s and 1960s as they were during 1990-2004, but took a major dip in the 1970s and 1980s during the period the AH technique was used. I asked Dr. Webster and Dr. Holland about the intense typhoon activity back in the 1950s and 1960s, and they argued that this activity was the result of high SSTs in the Northwest Pacific during that period. On his website, Kerry Emanuel argues that typhoon intensities were overestimated in the 1950s and 1960s. However, Knaff and Zehr (2006) make some convincing arguments that typhoon intensities during the 1973-1986 period were too low due to measurement error, and the number of Category 4 and 5 storms in the region have been roughly constant for the past 50 years. This paper has been accepted for publication in Weather and Forecasting, and will likely be published late this year. Dr. Knaff and Charles Sampson of the Naval Research Laboratory have performed a preliminary re-analysis of maximum typhoon intensities for the period 1966-1987 based on the Knaff and Zehr (2006) results, and this re-analysis will be presented at the upcoming 27th Conference on Hurricanes and Tropical Meteorology (April 24-28, 2006). They show that after correcting for the AH technique errors, the number of Category 4 and 5 typhoons during the 1966-1987 period increased by 1.5 per year, leaving only a slight upward trend in Category 4 and 5 typhoons during the period 1970 - 2004. The 16% increase in Category 4 and 5 typhoons found by Webster et al. during the past 15-year period is reduced to just 3%. Based on this new research, the results of Webster et al. may have to be modified. In particular, their global increase in storms from 1990-2004 compared to 1975-1989, as presented in that paper will be reduced from 57% to 42% if Dr. Knaff's typhoon re-analysis is accepted.


Figure 6. Number of Category 4 and 5 hurricanes in the Northwest Pacific Ocean since reliable records began in 1945. Data taken from the Joint Typhoon Warning Center "best track" database. Typhoon intensities from the period 1973 - 1986 were estimated using the "Atkinson-Holliday" (AH) technique, which may have underestimated typhoon intensity.

Northeast Pacific
Dr. Gray formulates the reasonable hypothesis that if one compares global major hurricane activity for the most recent ten years (1995-2004) with the previous ten years (1985-1994), one should see a significant difference, since global surface temperatures increased about 0.4� C between the two periods. He shows that the number of Category 3-4-5 hurricanes stayed exactly the same between these two periods--218 for each time period--if one excludes the Atlantic. I tabulated the results for just Category 4 and 5 hurricanes, and the results were very similar--135 storms storms globally (excluding the Atlantic) from 1985-1994, and 142 for 1995-2004. As most of you are aware, the Atlantic has seen a big increase in the number of intense hurricane the past ten years. Dr. Gray attributes to the Atlantic Multidecadal Oscillation (AMO), a natural cycle I discussed in an earlier blog. Dr. Gray offers another comparison, but just for Category 4 and 5 storms. The most reliable comparison one can make is using data from the Northeast and Northwest Pacific from the past 20 years. This excludes the issues of dealing with the natural AMO cycles in the Atlantic, and the poor data quality in the other ocean basins. Again, the data show essentially no difference between time periods. Indeed, when looking at the plot of Category 4 and 5 hurricane for the Northeast Pacific--the ocean area off the west coast of Mexico (Figure 7), and responsible for 19% of the world's Category 4 and 5 hurricanes--one sees no increasing trend in recent years.


Figure 7. Number of Category 4 and 5 hurricanes in the Northeast Pacific Ocean since reliable satellite intensity estimates began in 1970. Data taken from the National Hurricane Center "best track" database.

Atlantic
The Atlantic contributes only 9% of the world's Category 4 and 5 hurricanes, so is not much of factor when considering global numbers of these storms. Dr. Gray shows that the number of Category 4 and 5 hurricanes in the Atlantic has remained constant when one compares numbers from the past 15 years with an earlier active period from 1950-1964. However, this is a poor comparison. The period 1950-1964 fell entirely within a time when the warm phase of the AMO dominated the Atlantic, and had significantly enhanced intense hurricane activity (see Figure 8). The period 1990-2004 includes five years from the cold phase of the AMO, when intense hurricane activity was significantly down. Thus, comparison of 1950-1964 with 1990-2004 in the Atlantic is poor. One should make the comparison between data from the 11 years from the most recent warm phase of the AMO (1995-2005), and the previous warm AMO period we have good data for (1944-1969). This comparison shows that Category 4 and 5 hurricanes in the Atlantic have increased by 60% in the past 11 years compared to the previous active period 1944-1969. One can make a similar comparison for the cold phase of the AMO, contrasting the years 1970-1982 with 1983-1994. This comparison show no increase in Category 4 and 5 hurricanes for the later period with warmer SSts. I asked Dr. Landsea about the 60% increase in Category 4 and 5 hurricanes during the most recent warm phase of the AMO, and he thought that at least part of the increase could be explained by inadequate information from the Hurricane Hunters during that period. He explained that during that time, it was common in intense hurricanes for the Hurricane Hunters to get close enough to the eye to fix the storm on radar, but not actually penetrate through the eyewall into the eye. Who can blame them! The older aircraft like the DC-6 used during that time period were not safe to fly into Category 4 and 5 hurricanes. Dr. Landsea is working on a re-analysis project for the entire Atlantic hurricane database, but has only made it to the 1930s, and hopes to have a more definitive answer on the intensities of hurricanes during the 1950-1969 period in a few years.



Figure 8. Number of Category 4 and 5 hurricanes in the Atlantic Ocean since reliable aircraft reconnaissance intensity estimates began in 1944. Data taken from the National Hurricane Center "best track" database and not corrected for any suspected biases. The warm AMO periods are associated with enhanced intense hurricane activity, and are thought to be part of a natural decades-long cycle that affects only the Atlantic Ocean (as far as hurricane activity is concerned).

Conclusion
So who's right? Given the uncertainties in estimating tropical cyclone intensity presented by Drs. Gray, Landsea, and Knaff, plus the very large disagreement with the theory of hurricane intensification, it is unlikely that the large 80% increase in Category 4 and 5 hurricanes found by Webster et al. is real. There does appear to be some increase, but it is likely much smaller. Many troubling questions need to be answered, such as why comparison of the most recent ten years (1995-2004) with the previous ten years (1985-1994) shows almost no increase in Category 4 and 5 storms globally, during a period when a substantial increase in SST occurred.

All the scientists involved in this debate have stated the need for a rigorous re-analysis of all historical tropical cyclone data. However, there is currently little funding for such work. Dr. Knaff told me that his typhoon re-analysis work was unfunded, and that he did it because he felt strongly that the results of Emanuel (2005) and Webster et al. were inaccurate and needed to be challenged. Dr. Landsea's reanalysis of Atlantic storms is funded, but something he can only devote time to when his duties at NHC allow him. Dr. Knaff wrote me, "While I realize there are plans to reanalyze the Atlantic, the West Pacific, Southwest Pacific, and Indian Ocean are all being done piece by piece as part of several unfunded projects with little general support. If people are going to use the data for global studies, then NOAA, NSF or some other entity should fund a global reanalysis." I agree completely! Before I am willing to conclude that Category 4 and 5 hurricanes are indeed showing a significant increase, I want to see the science done with a better dataset, and covering a longer period of time. The NOAA Office of Global Programs or National Science Foundation needs to step in and fund this research.

While Category 4 and 5 hurricanes may indeed be increasing in frequency globally, one cannot yet say that global warming is the cause. Webster et al. close with the sentence, "attribution of the 30-year trends to global warming would require a longer global data record and, especially, a deeper understanding of the role of hurricanes in the general circulation of the atmosphere and ocean, even in the present climate state." Furthermore, global warming cannot be cited as the cause of recent intense storms, such a Hurricane Katrina, Hurricane Wilma, or Australia's Cyclone Larry and Cyclone Glenda.

Webster, Holland, and Curry have submitted another paper for publication titled, "Testing the Hypothesis that Greenhouse Warming is Causing a Global Increase in Hurricane Intensity". I'll be sure to review the paper when it comes out. In addition, earlier this month, the authors published another paper linking increasing SSTs to higher numbers of Category 4 and 5 hurricanes. The paper was called, "Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity", and I plan to say more about this paper in my next blog on the global warming-hurricane intensification debate. Later on this Spring, I'll also talk about the 2005 paper by Dr. Kerry Emmanuel of MIT in Nature that found increases in global hurricane duration and power dissipated due to increasing SSTs.

Be sure to tune in Tuesday, when the Colorado State University forecasting team founded by Dr. Bill Gray releases their updated 2006 hurricane season forecast.

Jeff Masters

References
Emanuel, K.A., "The dependence of hurricane intensity on climate", Nature, 326, 483-485, 1987.

Emanuel, K.A., "Increasing Destructiveness of Tropical Cyclones over the past 30 years, Nature, 436, 686-688, 4 August 2005.

Hoyos, C.D., P.A. Agudelo, P.J. Webster, and J.A. Curry, "Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity", www.scienceexpress.org, 16 March 2006, 10.1126/science.1123560.

Knaff, J.A., and R.M. Zehr, "Reexamination of Tropical Cyclone Wind-Pressure Relationships", accepted to Weather and Forecasting, 2006.

Knutson, T.R., and R.E. Tuleya, "Impact of CO2-Induced Warming on Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization," Journal of Climate 17, 18: 3477-3495, 2004. http://www.gfdl.noaa.gov/reference/bibliography/20 04/tk0401.pdf

Virmani, J.I., and R. H. Weisberg, "The 2005 hurricane season: An echo of the past or a harbinger of the future?", Geophysical Research Letters 33, L05707, 2006 doi:10.1029/2005GL025517.

Webster, P.J., G.J. Holland, J.A. Curry, and H.-R. Chang, "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", Science, 309, 1844,1846, 16 September 2005.





Climate Change

Updated: 21:01 GMT le 16 août 2011

Permalink

Glenda smashes into Australia

By: JeffMasters, 15:36 GMT le 30 Mars 2006

Tropical Cyclone Glenda smashed ashore near Onslow, Western Australia today as a Category 3 storm on the Saffir-Simpson scale, with maximum sustained winds of 115-120 mph, gusting to 155 mph, and a central pressure estimated at 940 mb by the Australian Bureau of Meteorology. A storm surge of at least 10 feet likely accompanied the storm to shore, but fortunately, Glenda missed the most heavily populated city of the region, Karratha, and damage will be far less than the $1 billion inflicted by Tropical Cyclone Larry just 11 days ago. The one-two punch of two major hurricanes hitting Australia in one year is not unprecedented; two Saffir-Simpson Category 4 hurricanes hit Queensland in 1918, killing 147 people, and twin Category 3 storms struck northern Queensland again between March 5 and 15, 1934, killing 64 people and causing $3 million in property and crop losses. The University of Wisconsin has an animation of Glenda hitting the coast.


Figure 1. Tropical Cyclone Glenda near landfall at 7:30 GMT March 30 2006, moving inland near Onslow on the Western Australian coast. This visible light image courtesy of the U.S. Navy.


An interesting article appears in The Australian today, where Dr. Bruce Harper, a consultant to the Bureau of Meteorology, said that Larry had been substantially overestimated in strength. A quote from the article:


Dr. Harper said, "It's not that there's any intention to exaggerate or there's anything wrong with the people at the bureau. It's just that the satellite recognition techniques they use are not accurate."

Bureau of Meteorology weather services supervisor Mike Bergin agreed Larry had not been as strong as the bureau claimed at the time.

"Tracking cyclones is a difficult exercise," Mr Bergin said. "These are dynamic things, changing all the time."

Dr. Harper claimed the bureau was not adequately resourced by the federal Government. He said Australia should follow the example of the US, which flew planes with recording instruments through hurricanes.


If you recall my blog from Monday discussing the problems with estimating hurricane strength in the Southern Hemisphere, these problems continue even today. This makes it very difficult to determine just how many Category 4 and 5 storms there really are, and whether or not they are increasing in number. I'll post part 2 of that discussion Friday, assuming today's severe weather outbreak in the U.S. doesn's grab the headlines. It could be a wild afternoon in the Plains, with the potential of strong F3 tornadoes, particularly in eastern Kansas and northeastern Oklahoma.

Jeff Masters

Updated: 17:53 GMT le 28 juin 2006

Permalink

Glenda takes aim at Australia

By: JeffMasters, 14:25 GMT le 29 Mars 2006

Tropical Cyclone Glenda has weakened to Category 3 storm on the Saffir-Simpson scale, with maximum sustained winds of 120 mph and a central pressure estimated at 920 mb by the Australian Bureau of Meteorology. While no longer one of the Southern Hemisphere's most intense tropical cyclones on record, Glenda is still a formidable storm likely to inflict heavy damage to the mining, oil, and gas industries along the Western Australian coast. The storm is expected to make landfall as a major Category 3 storm on the Saffir-Simpson scale Thursday. Fortunately, the region is sparsely populated, and significant upper-level winds associated with the jet stream should act to weaken Glenda just before landfall. Still, a 8 - 12 foot storm surge near and to the left of where the eye makes landfall can be expected. This was the approximate storm surge seen from Cyclone Vance in March 1999, a storm similar in strength and landfall location to Glenda. An impressive satellite animation of Glenda is available from the University of Wisconsin.


Figure 1. Tropical Cyclone Glenda at 6:30 GMT March 29 2006, moving southwest parallel to the Australian coast. This visible light image courtesy of the U.S. Navy.

Was Glenda the strongest tropical cyclone ever in the Southern Hemisphere?
The U.S. Navy estimated a central pressure of 898 mb yesterday for Glenda, which is the second lowest pressure I could find record of for the Southern Hemisphere. However, I doubt that this pressure will be considered official, since the Australian Bureau of Meteorology estimated a much higher minimum pressure of 910 mb. Unfortunately, the Joint Typhoon Warning Center does not make official pressure estimates. The record lowest pressure in the Southern Hemisphere is 879 mb, held by Cyclone Zoe of 2002, a Category 5 storm that affected several small islands in the Solomon chain. Reliable records of Southern Hemisphere cyclones only go back to the 1980s, so it is likely that there were other storms with lower pressures than Glenda in the Southern Hemisphere during the past century. The lowest pressure measured at the surface in a Southern Hemisphere cyclone was 905 mb at North Rankin A gas platform during Cyclone Orson on 22-23 April 1989. Orson had 160 maximum sustatined winds at the time, making it a Category 5 storm.

Jeff Masters

Updated: 17:54 GMT le 28 juin 2006

Permalink

An extraordinary Cat 5 in Australian waters

By: JeffMasters, 16:14 GMT le 28 Mars 2006

We've got a truly exceptional Category 5 tropical cyclone in the waters off of the Western Australia coast to discuss, so the continuation of my blog on whether the global number of Category 4 and 5 hurricanes are increasing will have to wait. Tropical Cyclone Glenda is a Category 5 storm on the Saffir-Simpson scale, with maximum sustained winds of 160 mph and a central pressure estimated at 898 mb by the U.S. Navy (910 mb by the Australian Bureau of Meteorology). A central pressure of 898 mb is the lowest pressure ever estimated for a Southern Hemisphere cyclone, at least that I could find record of. Reliable records go back to the 1980s. The lowest pressure ever estimated for a Southern Hemisphere cyclone was 900 mb, for Inigo of 2003 and Gwenda of 1998. Both were Category 4 cyclones on the Saffir-Simpson scale, and hit Western Australia in a location near where Glenda is expected to strike on Thursday. The lowest pressure measured at the surface in a Southern Hemisphere cyclone was 905 mb at North Rankin A gas platform during Cyclone Orson on 22-23 April 1989. Orson had 160 mph maximum sustatined winds at the time, making it a Category 5 storm.


Figure 1. Tropical Cyclone Glenda is moving southwest, parallel to the Australian coast. This visible light image courtesy of the U.S. Navy.

Two weeks after suffering an estimated $1 billion in damage from Cyclone Larry, Australia must brace for another strike from a major hurricane. The region of Western Australia likely to be threatened by Glenda is not heavily populated, but is home to many important mining, oil, and gas operations. Over 1,500 people were eveacuated earlier this year when Tropical Cyclone Clare battered the area with 70 mph winds. Oil and gas operations are already shutting down as Australia battens down again. Glenda is in a very favorable environment for continued intensification, with water temperatures averaging 30 C (86F) underneath, and very light wind shear. It is possible that later today Glenda will reach the highest winds ever recorded in the Southern Hemisphere, equalling the record of 150 knots (172 mph) estimated for Cyclone Daryl/Agnielle in November 1995. Increasing wind shear on Wednesday should act to weaken Glenda, but she is still expected to be a formidable Category 3 or higher storm at landfall (Category 5 on the Australian intensity scale, which goes by wind gust). Glenda is the sixth tropical cyclone this season for the Western Australia area. On average, five of these storms form during the season, which runs November through April.

Jeff Masters

Updated: 17:54 GMT le 28 juin 2006

Permalink

Are Category 4 and 5 hurricanes increasing in number?

By: JeffMasters, 16:36 GMT le 27 Mars 2006

In September 2005, a paper published in Science magazine reported that worldwide, the number of Category 4 and 5 hurricanes had increased 80% in the past 30 years. The paper, (Webster et al., 2005), titled "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", linked the rise in storms to increasing sea surface temperatures and concluded that "global data indicate a 30-year trend toward more frequent and intense hurricanes." The authors, led by Dr. Peter Webster of Georgia Tech and Dr. Greg Holland of the National Center for Atmospheric Research, argued that this was consistent with climate models that have predicted a future increase in frequency of the most intense hurricanes due to human-emitted greenhouse gases. This paper, along with another paper published in August, "Increasing Destructiveness of Tropical Cyclones over the past 30 years", by Dr. Kerry Emanuel of MIT, showing an increase in hurricane power and longevity in recent years, created a huge stir in the media. However, there is a large amount of uncertainty in the hurricane intensity data used by both papers, and their findings should be considered as preliminary evidence that the global incidence of Category 4 and 5 hurricanes may be increasing. There are good reasons to believe that the actual increase in Category 4 and 5 hurricanes is far lower than the 80% increase found by Webster et al.



Figure 1. Dr. Chris Landsea (right) and Dr. Greg Holland (left) presented their papers on the hurricane/global warming controversy at a January 31, 2006 session of the annual meeting of the American Meteorological Society. The standing-room only crowd was treated to a clash of opinions about whether hurricane intensity is being affected by global warming.

Other hurricane scientists disagree
The papers by Webster et al. and Emanuel have created considerable controversy in the hurricane science community. Many hurricane scientists disagree with the new results, and have disputed them in new papers submitted for publication. I will examine the arguments of three of these scientists here. Keep in mind that the Webster et al. paper went through peer review--it was revised based on the recommendations of at least two anonymous reviewers who read the paper before publication. The arguments of the other scientists disputing the paper have not been subject to peer review, and may have more errors or omissions than peer-reviewed work would have. The three scientists are:

Dr. Bill Gray of Colorado State University, who is famous for his successful long-range hurricane predictions and nearly 50 years of hurricane research and forecasting, submitted his critique to Science for publication, but the journal rejected it, since the document had already been published (on Dr. Gray's web site). Journals typically do not publish material that has been published elsewhere. In his abstract, Dr. Gray says: "I do not agree that global Category 4-5 tropical cyclone activity has been rising, except in the Atlantic over the last 11 years. The recent Atlantic upsurge has explanations other than global temperature rise".

Dr. Chris Landsea, Science and Operations Officer at the National Hurricane Center, chaired a standing-room only session exploring the hurricanes/global warming connection at the 2006 meeting of the American Meteorological Society (AMS). He presented a talk with additional evidence supporting Dr. Gray's position.

Dr. John Knaff, a hurricane researcher at the NOAA/Cooperative Institute for Research in the Atmosphere Colorado State University, has performed an extensive re-analysis of Northwest Pacific typhoons, and questions the intensity estimates used by Webster et al. for typhoons during the period 1966-1987. His paper, "Reexamination of Tropical Cyclone Wind-Pressure Relationships" has been accepted for publication to Weather and Forecasting, and will probably be published in late 2006.

Who are Webster et al.?
Lets examine the credentials of the Science paper's authors. The primary author, Dr. Peter Webster of Georgia Tech, holds a Ph.D. from MIT and has received the most prestigious award issued by the American Meteorology Society--the Carl Gustav Rossby Research award. Webster's primary expertise is not hurricanes--he has mostly studied monsoons. However, the second author, Dr. Greg Holland of the National Center for Atmospheric Research, is a hurricane expert. He earned his Ph.D. in 1983 at Colorado State as a student of Dr. Bill Gray, and has authored over 100 hurricane-related journals articles or book chapters. One of the other co-authors, Dr. Judith Curry, is the Chair of the Georgia Tech School of Earth and Atmospheric Sciences. So, the paper's authors have a track record of producing high-quality research that should be taken seriously.

The theoretical basis for connecting hurricane intensity and global warming
Hurricanes act as giant heat engines, so it is logical to assume that an increase in sea surface temperatures (SSTs) will make more intense hurricanes. Indeed, there is a general consensus among hurricane scientists that an increase in SSTs due to global warming, should, in theory, lead to more intense hurricanes. Theory predicts that hurricane wind speeds should increase about 5% for every 1 degree Centigrade increase in tropical ocean temperature (Emanuel, 1987). Computer models confirm this tendency, but assign a slightly smaller magnitude to the increase (Knutson and Tuleya, 2004). Given the expected 1.5� to 4.5� C warming of Earth's climate expected by 2100, theory predicts a gradually increasing frequency of Category 4 and 5 storms.

Global warming in the past century has increased ocean temperatures about 1�F (0.5�C) which should correspond at most to about a 2.5% increase in hurricane wind speeds. If this theory is correct, an upper-end Category 3 hurricane with wind speeds of 130 mph--like Hurricane Katrina at landfall--owes 2-3 mph of its sustained winds to global warming. Hurricane wind speeds are estimated to the nearest 5 knots (5.8 mph), and one can get a general idea of what percent increase we've seen in Category 4 and 5 hurricanes due to global warming by looking at the number of high end Category 3 hurricanes (winds of 130 mph) and low end Category 4 hurricanes (135 mph winds). If we assume a 2-3 mph increase in winds of these storms is due to global warming over the past 35 years, one would expect to see a 5% increase at most in Category 4 and 5 hurricanes. An increase this small is not detectable given the current accuracy of estimating hurricane winds, and the relatively few number of of these storms that occur each year. This expected maximum 5% increase is quite a disagreement with the 80% increase found by Webster et al.! So, either the measurements are wrong, or the theory is wrong--or a combination of the two. I believe it may well be a combination of the two. The fact that the originator of the intensity theory (Kerry Emanuel) is one of the scientists who is advocating that the theory may be in error, is reason enough to doubt the theory. The formation and intensification of hurricanes are not well understood, and it would be no surprise if major revisions to intensity theory are made in the future. However, such a wide difference between the theory and the reported trends should make us suspicious of the observed data, as well.

Sea Surface Temperatures have increased since 1970
Webster et al. show a plot (Figure 2) of the sea surface temperature (SST) in the six major ocean basins that support tropical cyclones. Since 1970, SSTs in all the oceans have risen by up to .5� C. The paper chooses to look only at the period from 1970 to the present, since 1970 is the approximate time when global satellite measurements of tropical cyclone intensity became available. Before 1970, there are reliable intensity measurements only in the Atlantic and Northwest Pacific, thanks to the Hurricane Hunters. These measurements began in 1944 in the Atlantic and 1945 in the Northwest Pacific (but stopped in 1987 in the Pacific).



Figure 2. Running 5-year mean of SST during the respective hurricane seasons for the principal ocean basins in which hurricanes occur: the North Atlantic Ocean (NATL: 90� to 20�E, 5� to 25�N, June-October), the Western Pacific Ocean (WPAC: 120� to 180�E, 5� to 20�N, May-December), the East Pacific Ocean (EPAC: 90� to 120�W, 5� to 20�N, June-October), the Southwest Pacific Ocean (SPAC: 155� to 180�E, 5� to 20�S, December-April), the North Indian Ocean (NIO: 55� to 90�E, 5� to 20�N, April-May and September-November), and the South Indian Ocean (SIO: 50� to 115�E, 5� to 20�S, November-April). Reprinted with permission from SCIENCE 309:1844-1846 � 2005 AAAS. Permission from AAAS is required for all other uses.

The global number of hurricanes has not increased

Webster et al. also present plots of the global frequency of tropical storms, hurricanes, and the number of days those storms are present (Figure 3). No trend is apparent in these plots, and the paper states that "against a backdrop of increasing SST, no global trend has yet emerged in the number of tropical storms and hurricanes." So far, all hurricane scientists are in agreement.



Figure 3. Global time series for 1970-2004 of (A) number of storms and (B) number of storm days for tropical cyclones (hurricanes plus tropical storms; black curves), hurricanes (red curves), and tropical storms (blue curves). Contours indicate the year-by-year variability, and the bold curves show the 5-year running average. Reprinted with permission from SCIENCE 309:1844-1846 � 2005 AAAS. Permission from AAAS is required for all other uses.

An 80% increase in Category 4 and 5 hurricanes?

Webster et al. present a plot (Figure 4) where of the number of Category 1, Category 2 and 3, and Category 4 and 5 storms, averaged into 5-year "pentads". The results show little change in the statistics of Category 1, 2, and 3 hurricanes, but a startling increase in Category 4 and 5 hurricanes. These most intense and dangerous storms on Earth have increased from 50 per five-year period in the 1970s, to 90 in the past decade--a near doubling!



Figure 4. Intensity of hurricanes according to the Saffir-Simpson scale (categories 1 to 5). (A) The total number of category 1 storms (blue curve), the sum of categories 2 and 3 (green), and the sum of categories 4 and 5 (red) in 5-year periods. The bold curve is the maximum hurricane wind speed observed globally (measured in meters per second). The horizontal dashed lines show the 1970-2004 average numbers in each category. (B) Same as (A), except for the percent of the total number of hurricanes in each category class. Dashed lines show average percentages in each category over the 1970-2004 period. Reprinted with permission from SCIENCE 309:1844-1846 � 2005 AAAS. Permission from AAAS is required for all other uses.

An 80% increase in Category 4 and 5 hurricanes? Not!

Here's where the critics of Webster et al. differ. Let's look at the criticisms one ocean basin at a time. First: the Southern Hemisphere oceans, and the part of the Indian Ocean in the Northern Hemisphere. These regions are responsible for 25% of the world's Category 4 and 5 hurricanes. Dr. Gray criticizes the quality of the data in the Indian Ocean and Southern Hemisphere ocean basins during the period 1975-1989, remarking: "In the late 1970s I visited all the global tropical cyclone centers and observed their satellite capabilities and the training of their forecasters as part of a World Meteorological Organization (WMO) tropical cyclone trip that I was commissioned to make. The satellite tools and forecaster training in the tropical cyclone regions of the Indian Ocean and Southern Hemisphere during the 1975-1989 period was not adequate for the task of objectively distinguishing Category 4-5 hurricanes from Category 3 hurricanes or to always be able to confidently distinguish Category 4-5 hurricanes from Category 1-2 hurricanes." Dr. Gray does not provide any details about how how this lack of training could have led to a systematic error in classifying too few storms at Category 4 and 5 intensity. However, Dr. Landsea did cite an example of this in his talk at the 2006 American Meteorological Society meeting--for a number of years after 1974's Tropical Cyclone Tracy devastated Darwin, the Australians never assigned an intensity higher than Tracy to any storm because they believed Tracy was the strongest a storm could be in the Australian region. Tracy was a weak Category 4 cyclone with 135 mph winds and a 954 mb pressure. This was a false assumption, as many cyclones stronger than Tracy have formed in Australian waters.

This brings up the most serious weakness in the Webster et al. paper--they do very little discussion of the uncertainty in hurricane intensity measurements. Hurricane intensity is characterized by a 1-minute measurement of maximum sustained winds at ten meters above the surface. In practice, this quantity is virtually never measured, but must be inferred indirectly from other measurements. All of these inferred measurements of wind speeds have errors. Satellite estimates of hurricane intensity are often wrong by a full category on the Saffir-Simpson scale--or even two categories. This is particularly true when there are only two geostationary satellites covering the Earth, as was the case for much of the 1970s, and part of the 1980s. I learned this the hard way during my stint with the Hurricane Hunters when I flew into Hurricane Hugo in 1989 expecting a Category 3 hurricane based on satellite estimates. The problem was that one of the GOES satellites had failed earlier that year, leaving just one satellite to cover all of the U.S. and Atlantic Ocean. This one satellite was positioned much farther west in order to see all the way to California, and thus had a poor, oblique view of hurricanes out over the Atlantic. If a satellite can't see all the way to the bottom of the eye of a hurricane because of an oblique viewing angle, it will come up with an eye temperature that is too cool, and thus an intensity estimate that is too low. Hugo turned out to be a Category 5, and made us pay dearly for our mistake. Similarly, a systematic underestimation of hurricane intensities in the 1970s is quite possible, due to the oblique viewing angle that the relatively few geostationary satellites afforded during that period.

Furthermore, Dr. Landsea argued, the technique used to perform satellite estimation in all ocean basins of hurricane intensity (the Dvorak technique) did not even get invented until 1972--two years after the start of the data used by Webster et al. It wasn't until 1984 that the Dvorak technique was extended to infrared satellite imagery. So, between 1972 and 1984, all satellite hurricane intensity estimates were done on visible satellite imagery, and were unavailable at night. In addition, measurement errors from the first generation of infrared satellite instruments was much higher, since their resolution was a relatively poor 9 km--compared to the 4 km resolution of today's instruments. Dr. Landsea called for a major re-analysis effort of the old satellite photos from the 1970s and 1980s to try to quantify some of these errors. He argued that his preliminary look at old satellite images from the Northern Indian Ocean from 1970 to 1989 had already revealed five additional storms that may have been Category 4 or 5. Webster et al. found only one Category 4 or 5 hurricane for this time period there. Dr. Landsea suggested that until a full re-analysis took place in all ocean basins, the quality of the historical global hurricane intensity data was not high enough to be able to see a possible increase in the number of Category 4 and 5 hurricanes.



Figure 5. Number of Category 4 and 5 hurricanes in the Indian Ocean and Southwest Pacific Ocean (off the east coast of Australia) since 1970. A a rather dramatic rise in recent years is apparent. Data from 1970-2002 are taken from a reanalysis of available data from Australia, Fiji, and the Joint Typhoon Warning Center, done by Charlie Neumann. All the data used in the Webster et al. study are available from Dr. Judith Curry's web page.

Dr. Holland spoke after Dr. Landsea, and agreed that a major re-analysis effort was needed in order to help quantify some of the errors in hurricane intensities. He rebutted Dr. Landsea's arguments by pointing out that given the very large rise in Category 4 and 5 hurricanes in the Southern Hemisphere and Indian Oceans, about 50% of all Category 1 and 2 hurricanes would have to be re-analyzed as Category 4 and 5 storms to invalidate their results in that region. While acknowledging the the data was bad in the 1970s, he maintained that nobody thought it was that bad.

Summary of the Southern Hemisphere and Indian Ocean data

If we restrict ourselves to just looking at the Southern Hemisphere and Indian Ocean data since 1989--the date when everyone agrees that the data quality is reasonable--there is not enough data to be sure of any kind of trend (Figure 5). So until better intensity estimates of hurricanes in the Indian Ocean and Southern Hemisphere ocean basins from 1970-1989 are available, one should view the results of Webster et al. with caution for these regions. Still, there is such a large increase in Category 4 and 5 hurricanes that it is unlikely that re-analysis will find that all of this increase in unreal.

--To be continued Tuesday afternoon--

Jeff Masters

References
Emanuel, K.A., "The dependence of hurricane intensity on climate", Nature, 326, 483-485, 1987.

Emanuel, K.A., "Increasing Destructiveness of Tropical Cyclones over the past 30 years, Nature, 436, 686-688, 4 August 2005.

Knaff, J.A., and R.M. Zehr, "Reexamination of Tropical Cyclone Wind-Pressure Relationships", accepted to Weather and Forecasting, 2006.

Knutson, T.R., and R.E. Tuleya, "Impact of CO2-Induced Warming on Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization," Journal of Climate 17, 18: 3477-3495, 2004. http://www.gfdl.noaa.gov/reference/bibliography/20 04/tk0401.pdf

Webster, P.J., G.J. Holland, J.A. Curry, and H.-R. Chang, "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", Science, 309, 1844,1846, 16 September 2005.

Climate Change

Updated: 21:18 GMT le 16 août 2011

Permalink

Hurricane Rita final report issued

By: JeffMasters, 14:03 GMT le 24 Mars 2006

The National Hurricnae Center has released its final report on Hurricane Rita. The report revises Rita's strength at landfall downward by 5 mph. Doppler radar data not available at the time the storm hit suggests that Rita's peak winds were 115 mph, not 120 mph as was previously thought. However, Rita was still a tremendously strong Category 3 hurricane at landfall, and carried a storm surge characteristic of a Category 4 hurricane with her to shore. The NHC report mentioned that storm surge values were hard to figure out, since most of the tidal gauges were destroyed. A maximum storm surge of 15 feet and perhaps a few feet higher probably occurred along the Louisiana coast to the right of where the eye came ashore. This storm surge destroyed nearly every building in the towns of Holly Beach, Cameron, Creole, and Grand Cheniere. The surge reached up to 30 miles inland in same locations, and flooded downtown Lake Charles-- with up to six feet of flood waters. Rita's central pressure at landfall is estimated at 937 mb based on dropwindsonde data from the Hurricane Hunters. This landfall pressure is the lowest on record in the Atlantic basin for a Catgegory 3 hurricane with 115 mph winds. Similar to Katrina one month earlier, the relatively weak winds in Rita for such a low pressure resulted from the fact that Rita grew to enormous size, spreading its broad pressure field over a huge area.


Figure 1. The eye of Hurricane Rita shortly after reaching its peak intensity. Rita had 180 mph winds and the 4th lowest sea-level pressure on record, 895 mb. Image taken from the NASA's MODIS satellite.

Rita's peak intensity while out over the warm waters of the Gulf of Mexico's Loop Current was higher than previously thought--the maximum winds were 5 mph stronger, and the central pressure 2 mb lower. There was a 6-hour gap in hurricane reconnaisance flights during the time that Rita underwent its rapid deepening phase, and it is thought the the storm continued to strengthen for a few hours while there was no one there to see it. Rita's maximum winds are now estimated at 180 mph, and her lowest pressure, 895 mb. This is the fourth-lowest pressure on record in the Atlantic, behind 882 mb in Wilma (2005), 888 mb in Gilbert (1988), and 892 mb in the 1935 Florida Keys hurricane. Rita's pressure dropped an astonishing 70 mb in just 24 hours, and strengthened from a tropical storm to a Category 5 hurricane in less than 36 hours just after it passed 70 miles south of the Florida Keys. We are very fortunate that this deepening phase did not start 24 hours earlier and the storm did not track 70 miles further north, or else the U.S. might have had two hurricane disasters with major loss of life in 2005. The Florida Keys need a full 72 hours of evacuation time to get everybody out, and the evacuation order would likely have been given only 24 hours in advance. Next to New Orleans, the Keys are the number one most vulnerable place in the U.S., and a storm that causes major loss of life there is probably only a matter of time.

Jeff Masters


Figure 2. Radar image of Hurricane Rita as it began its explosive deepening to a Category 5 hurricane, barely sparing the Florida Keys.

Updated: 17:56 GMT le 28 juin 2006

Permalink

New Category 5 record for the Hurricane Season of 2005

By: JeffMasters, 16:21 GMT le 22 Mars 2006

The astounding Hurricane Season of 2005 has extended its grip on the record for most Category 5 hurricanes in a season. According to the National Hurricane Canter report on Hurricane Emily released earlier this month, Emily is now recognized as a Category 5 hurricane. This brings the record for most Category 5 hurricanes in a season to four (Emily, Katrina, Rita, and Wilma). The old record was two Category 5 storms, set in 1960 and again in 1961. Emily is the earliest-forming Category 5 hurricane on record in the Atlantic basin and the only known hurricane of that strength to occur during the month of July.

According to the report, Emily was a Category 5 hurricane with 160 mph winds and a 929 mb central pressure for about six hours at 00 GMT July 17 2005, while located approximately 115 miles southwest of Jamaica. The storm weakened somewhat before making landfall on the Mexican coast near Cozumel Island as a Category 4 storm with 135 mph winds and a storm surge of up to 15 feet. Emily went on to cross the Gulf of Mexico and slam ashore on the Mexican coast south of Brownsville, Texas, as a Category 3 hurricane. Emily killed one person on its passage over Grenada as a Category 1 hurricane, and five in Jamaica. Amazingly, no one died in Mexico as a result of these two powerful hurricane strikes on the coast--a tribute to the successful evacuation efforts by the Mexicans. In addition, Mexico suffered only four deaths from Hurricane Wilma's four-day pounding. Wilma started out as a Category 4 hurricane when it hit Cozumel Island, and gradually weakened to a Category 2 hurricane as it plowed north over Cancun and eventually into the Gulf of Mexico. Mexico's feat of surviving two Category 4 hurricane strikes and a Category 3 strike to populated areas, with only four deaths, is a civil defense success unparalleled in hurricane history.


Figure 1. Hurricane Emily at its peak strength--a Category 5 storm with 160 mph winds.

One other interesting item to note about Emily: the official NHC track forecast out to four days was better than any of the computer forecast models. Five-day forecasts by a few of the models such as the GFS were better than the official forecast, though. In general, the official NHC forecast was tough to beat over the course of the Hurricane Season of 2005.

Jeff Masters

Updated: 16:23 GMT le 22 Mars 2006

Permalink

Australia cleans up from Larry

By: JeffMasters, 18:00 GMT le 21 Mars 2006

Emergency work continues in the Queensland territory of Australia, where Tropical Cyclone Larry roared ashore Sunday near the town of Innisfail as a major Category 3 hurricane with sustained winds of 118 mph and gusts to 180 mph. Larry caused tremendous damage to crops and buildings, causing at least $400 million in damage and leaving 7000 people homeless. Fortunately, no deaths or major injuries occurred. Larry may be the strongest tropical cyclone to affect the east coast of Australia, and the most damaging cyclone to affect Australia since Tropical Cyclone Tracy devastated Darwin on Christmas Eve in 1974, killing 71 and leaving 20,000 homeless.

Media reports continue to confuse people by referring to Larry as a Category 5 storm, and not clarifying that this was on the Australian severity category system, a one to five ranking system based on the maximum wind gusts of a storm. A storm that has wind gusts in excess of 174 mph (280 km/h) is classifed as a Category 5. In the U.S. Saffir-Simpson scale that we are familiar with, the strength of a storm is based on the sustained winds, not the gusts. According the Australian Bureau of Meteorology, Tropical Cyclone Larry at landfall had 118 mph sustained winds. Adam Moyer, a grad student at Penn State, just pointed out to me that the Australians use a 10-minute average to report their sustained winds, while the U.S. NHC uses a 1-minute average. Thus, the sustained 1-minute average wind speeds of Larry were probably closer to 130 mph--the high end of the Category 3 range on the Saffir-Simpson scale. Category 3 sustained wind speeds range from 111 to 130 mph. However, the maximum 1-minute sustained winds as estimated by the Joint Typhoon Warning Center were 115 mph, gusting to 145 mph. The Australians and the Joint Typhoon Warning Center both maintain their own "official" data bases of tropical cyclones, so we can see that for Larry these will disagree. This disagreement highlights some of the problems researchers who are attempting to make a connection between global warming and hurricane intensity have--which "official" data base do you use for the Southern Hemisphere? You get a different answer depending upon which database you use.


Figure 1. Tropical Cyclone Wati off the coast of Australia as a minimal hurricane with 75 mph winds.

What's up next for Australia?
Currently, Tropical Cyclone Wati (a Category 1 hurricane on the Saffir-Simpson scale), is just off the east coast of Australia in a location similar to where Larry came ashore. Wati is expected to recurve to the south and weaken over the next three days, but may come close enough to the coast for warnings and watches to be issued. On Australia's west coast, there is Tropical Storm Floyd to worry about. Floyd is expected to become a Category 2 hurricane by Thursday.

The Southern Hemisphere tropical cyclone season runs November through April, and there should be only one or two more tropical cyclones this Spring in the Southwest Pacific (off of the east coast of Australia) and the southern Indian Ocean (off of the west coast of Australia). So far, the hurricane season in the Southwest Pacific has been about average, and the hurricane season in the South Indian ocean has been below average.

For the Southwest Pacific so far this hurricane season, here are the storm numbers, followed by averages in parentheses:

Tropical storms: 7 (9)
Hurricanes: 4 (5)
Major hurricanes, Cat 3-4-5: 1 (2)

And for the South Indian ocean:

Tropical storms: 12 (17)
Hurricanes: 4 (9)
Major hurricanes, Cat 3-4-5: 3 (5)

Jeff Masters

Updated: 17:56 GMT le 28 juin 2006

Permalink

Larry strikes Australia

By: JeffMasters, 14:57 GMT le 20 Mars 2006

Tropical Cyclone Larry roared onto the coast of eastern Australia Sunday near the town of Innisfail as a major Category 3 hurricane with sustained winds of 118 mph and gusts to 180 mph. Although no deaths or serious injuries were reported, Larry caused tens on millions of dollars in damage to structures and crops in a part of Australia unused to seeing severe tropical cyclones. Innisfail is a popular jumping-off point for tourists heading to the Great Barrier Reef, and Larry will be a severe blow to the economy. The reef itself suffered a direct hit from the cyclone, but the extent of damage is unknown.

Larry may be the strongest tropical cyclone in recorded history to hit the east coast of Australia. The north coast and west coast of Australia are more prone to major hurricanes, and just last year Tropical Cyclone Ingrid hit Croker Island in the Gulf of Carpenteria off the northern coast of Australia as a Category 3 hurricane of strength similar to Larry.


Figure 1. Tropical Cyclone Larry at landfall in Australia.

As bad as Larry was, the media coverage I saw yesterday on several news web sites was over-hyped. All of the major media reports I saw called Larry a Category 5 storm with winds up to 180 mph, and one report said it could become "Australia's Katrina". What they didn't mention was that Australian tropical cyclones are ranked by the Australian severity category, a one to five ranking system based on the maximum wind gusts of a storm. A storm that has wind gusts in excess of 174 mph (280 km/h) is classifed as a Category 5. In the U.S. Saffir-Simpson scale that we are familiar with, the strength of a storm is based on the sustained winds, not the gusts. Tropical Cyclone Larry at landfall had 118 mph sustained winds, which made it a low-end Category 3 storm on the Saffir-Simpson scale--Category 3 sustained wind speeds range from 111 to 130 mph. Larry's lowest pressure was 925 mb (same as hPa, hecto-pascals, which the Australians use as their pressure unit). Katrina at its maximum intensity had maximum sustained winds of 175 mph, with gusts to 215 mph, and a minumum pressure of 902 hPa (mb).

The Southern Hemisphere tropical cyclone season runs November through April. The waters in the Southern Hemisphere oceans have reached their peak temperatures, and are now starting to cool. There is another storm, Tropical Cyclone Wati, that is near the Australian Coast in the same region as Larry stuck, but Wati is expected to recurve out to sea and weaken over the next three days.

Jeff Masters

Updated: 17:57 GMT le 28 juin 2006

Permalink

Hawaii gets a temporary reprieve

By: JeffMasters, 16:40 GMT le 17 Mars 2006

The rains have stopped for the past day on Hawaii's Kauai Island, where over 100 inches of rain has fallen in the mountains in the past three weeks. The heavy rains are due to a persistent upper-level low pressure system, a common occurence in the Central Pacific during a La Nina event like the region is now experiencing. The rains moved away from the islands yesterday, which have been under a continuous series of flash flood warnings and watches for weeks. The improved weather will aid in the search for victims of the failure of an earthen dam that burst on Kauai Tuesday. When the dam broke, a 20-foot flood of water moving at 15-20 mph smashed through a populated area, killing two and leaving six people missing and presumed dead. If the missing people are declared dead, this week's disaster would be the deadliest weather disaster in Hawaii's history.

Figure 1. Radar estimated precipitation on Kauai from March 13 - March 17. The radiating rays to the north are caused by mountains that block the radar beam, and the actual precipitation on the northern part of the island is greater than shown here.

Hawaii is probably the safest state as far as deaths from weather-related causes go. High surf is the leading cause of weather-related deaths in Hawaii, with 92 deaths between 1960-2004. Flash floods have killed 46 people in Hawaii in the past 45 years, high wind, six people, and hurricanes, six. Prior to this week's flood disaster, the previous most deadly flood disaster on Hawaii occurred on December 14, 1991, when a rainstorm dropped over 20 inches of rain in 12 hours on Kauai, causing five deaths, intense flooding, bank failures, erosion, and slides, with more than $5 million in property damages. Hawaii's only billion-dollar weather disaster occurred in 1992, when Hurricane Iniki passed directly over Kauai as a Category 4 hurricane, killing 6 and causing over $3 billion in damage. Hurricanes are fairly rare in Hawaii--only three hurricanes have brought hurricane-force winds over the islands since 1957. The National Climatic Data Center lists Hawaii as having the second fewest billion dollar weather disasters of any state since 1980 (one). Only Alaska has had no billion-dollar weather disasters.

The 100+ inches of rain that fell on Kauai's Mt. Waialeale the past three weeks has not set any records yet--Mount Waialeale averages 424 inches of rain per year, and is second only to the the monsoon-drenched Himalaya Mountains of India as the wettest spot on Earth. Mt. Waialeale recorded 683 inches of rain in 1982. The U.S. record of 704 inches in a year was set the same year at nearby Maui Island's Puu Kukui, at 5,788 feet elevation. The Hawaiian state 24-hour rainfall record is 38 inches at Kilauea Plantation on the island of Kauai, on Jan 24-25, 1956. Mt. Waialeale has three factors that help it catch more rain than other locations in the Hawaiian islands (thanks, Wikipedia):

1) Its northern position relative to the main Hawaiian Islands provides more exposure to frontal systems that bring rain during the winter.
2) It has a relatively round and regular conical shape, exposing all sides of its peak to winds and the moisture that they carry.
3) Its peak lies just below the so-called trade wind inversion layer of 6,000 feet (1,800 m), above which trade-wide-produced clouds cannot rise.

The long range outlook for Kauai and the rest of the Hawaiian islands is not good--another upper-level low pressure system is expected to move over the islands Saturday, bringing an increased chance of flash flooding. The rains are part of a typical La Nina weather pattern for the Hawaiian islands which is expected to continue for several months, according to the latest seasonal outlook issued yesterday by the Climate Prediction Center.

Jeff Masters

Flood

Updated: 23:04 GMT le 16 août 2011

Permalink

F4 tornado reported; Brazilian disturbance fizzles

By: JeffMasters, 14:27 GMT le 16 Mars 2006

Violent tornadoes--one rated F4 or F5 on the Fujita scale--are extremely rare. Only one was reported last year, the F4 November 15, 2005 tornado that injured 37 people when it swept through Madisonville, Kentucky. A damage survey completed yesterday afternoon revealed that a violent F4 tornado crossed through Monroe County, Missouri on the evening of March 12. Winds from the tornado were estimated at the lower end of the F4 scale (208-260 mph). The F4 rating was given after meteorologists found a well-built home that had been completely leveled, with debris from the home carried over 1/2 mile away. A pickup truck at the home was lifted and tossed over 100 yards into the living room of an adjacent home. Fortunately, the tornado was much weaker (F1 - F2) when it plowed through the nearby town of Monroe.

Damage surveys from the March 11-13 tornado outbreak still continue, and it is still uncertain how many tornadoes occurred. I wouldn't be surprised if the outbreak turns out to be the largest of the year--the average number of tornadoes for the entire month of March is only 63, and we came close to that in one weekend! However, with the April-June peak of tornado season still to come, we can expect a lot more severe weather this Spring. Severe weather may resume on Tuesday, when the first of a series of major storm systems is expected to move across the country. These systems will also bring a small measure of drought relief to some drought-stricken areas of Texas, Arizona, and surrounding states.

Brazilian disturbance fizzles
The tropical disturbance that was off the Brazilian coast yesterday has lost all of its deep convection, and is now just a swirl of low clouds. No further development of this system is likely--wind shear remains too high to allow deep convection to reform over this low. Climatologia Urbana de Sao Leopoldo, a private weather center in the southernmost state of Rio Grande do Sul in Brazil, has posted a detailed analysis of this system. It helps if you can read Portugese!

Jeff Masters

Tornado

Updated: 18:51 GMT le 05 janvier 2012

Permalink

Brazilian tropical disturbance, and tornado damage surveys

By: JeffMasters, 19:23 GMT le 15 Mars 2006

The season's second South Atlantic tropical/sub-tropical disturbance has formed off of the coast of Brazil today. The disturbance formed from the remains of a cold-core low, which sat over warm waters of 27 degrees C long enough to start acquiring tropical characteristics. We saw this same behavior this past hurricane season with the Greek storms Delta, Epsilon, and Zeta. The disturbance is mostly just a swirl of low clouds, but has seen two bursts of deep convection today. The most recent burst of convection, seen in the satellite photo below, formed in a spiral band well removed from the center. Early this morning, a more impressive burst of deep convection formed near the storm's center, but was quickly ripped away by strong westerly upper-level winds. These strong winds are expected to continue to bring high levels of wind shear over the disturbance over the next few days, and likely keep it from forming into a tropical depression. The system is expected to move slowly southwest, parallel to the Brazilian coast, and get absorbed into a frontal system to the south by Friday. No threat to land is likely, and this storm is mostly just of academic interest.


Figure 1. Tropical/subtropical disturbance off the coast of Brazil. Image credit: NASA Global Hydrology and Climate Center.

So, the academic question to ask is, does this second tropical system of the year off the coast of Brazil show that climate change is affecting the Atlantic? Only one hurricane and two tropical depressions have been observed in the South Atlantic since 1970, when accurate tracking methods became available with the advent of weather satellites. There is usually too much wind shear to allow a tropical cyclone to form, and the South Atlantic lacks an active "Intertropical Convergence Zone" (ITCZ)--that stormy band of weather that stretches along the Equator and acts as a source region for many of the disturbances that grow into Northern Atlantic hurricanes. With Hurricane Catarina of March 2004, another tropical depression in January 2004, a "near miss" tropical cyclone February 24 of this year, and now another tropical or subtropical system trying to form in the South Atlantic today, it is quite possible that climate change might be to blame. It may also be that we are seeing an active period in the South Atlantic that has a long cycle, and last repeated itself before satellites were around. Given the Atlantic Multi-decadal Oscillation (AMO) that affects hurricane activity in the North Atlantic, it is reasonable to think we might see a similar pattern in the South Atlantic.

In either case, I believe is it time that the NHC considered adopting a naming system for the South Atlantic. Had today's system intensified into a tropical storm, it would not have been given a name, since there is no naming system in place for the South Atlantic Ocean. Given the current trends we're seeing, it would be no surprise if we saw more tropical systems here in the next few years.

Tornado damage surveys from the weekend's outbreak
More damage surveys are complete from the weekend's major tornado outbreak, and it now appears that the strongest tornadoes were of F3 intensity on the Fujita scale. There were at least four F3 tornadoes in the outbreak, and these tornadoes had winds in the 158 - 206 mph range (roughly the same winds as found in a Category 5 hurricane). The Springfield, MO NWS office has posted a detailed summary of the the three F3 tornadoes that affected the southwestern portion of Missouri over the weekend, and the Central Illinois NWS office has posted a nice summary of the two F2 tornadoes that slammed Springfield, IL on Sunday, March 12. Included are zoom radar animations of the impressive hook echo, plus many damage photos. Not all the tornado-like damage from the weekend's wild weather was due to tornadoes, though--a storm survey done in along the west side of the Quad City Airport in Moline from Sunday concluded that the damage from a 107 mph wind gust done to homes, trees, and power lines on the west side of the airport was due to a severe thunderstorm downdraft (microburst).

Jeff Masters

Tornado

Updated: 18:54 GMT le 05 janvier 2012

Permalink

March madness

By: JeffMasters, 16:22 GMT le 14 Mars 2006

Violent tornadoes of up to F3 intensity ripped through Missouri, Illinois, and many other states over the weekend, according to preliminary damage surveys conducted by the National Weather Service. The first violent tornado on Saturday that struck St. Mary, MO and killed two people was an F3 tornado (158-206 MPH). Ironically, the two were killed as they fled the tornado in their car. They drove directly into the tornado, which hurled their car into a large propane storage tank. Their house survived the storm--more evidence of why you take shelter in a building during a tornado, and not try to escape in your car.

Two tornadoes struck Springfield, IL on Sunday night, and both were rated as F2 tornadoes with 120 mph winds, according to an NWS storm survey performed yesterday. The tornadoes were over a half mile wide at times, and had damage paths 5.5 and 4 miles long, respectively.

A supercell produced an F3 tornado (158-206 MPH) with a 31 mile long path in Webster County, Missouri. Another F3 tornado with a 40 mile long track passed through mostly rural land between Verona and Christianville, MO. An F2 tornado hit Gravois Mills, and numerous other F0 and F1 tornadoes also passed through Missouri. Damage surveys are not yet complete for some of the other violent tornadoes that affected the area, but I will pass along the results when they become available.

FUJITA SCALE:

F0 40 MPH TO 72 MPH
F1 73 MPH TO 112 MPH
F2 113 MPH TO 157 MPH
F3 158 MPH TO 206 MPH
F4 207 MPH TO 260 MPH
F5 261 MPH TO 318 MPH

March Madness forecast contest
If you want to try your luck (or skill) at forecasting, The University of Michigan's Department of Atmospheric, Oceanic, and Space Science is sponsoring its annual "WeatherDance" forecasting contest for the duration of the NCAA basketball tournament. The object is to forecast which of the two teams' campuses will be warmer (or cooler, it alternates between rounds) on the day of the tournament game. Hence the teams that advance in the Weather Tournament will not necessarily be the same teams that advance in the basketball tournament. You can play the men's or women's bracket, or both. It is free to participate--register at weatherdance.org to play. One Grand Prize winner will be the guest of the University of Michigan on an expense-paid tornado chase May 29-June 2 in Tornado Alley (but must be at least 18 years of age). Sixteen additional participants will win signed copies of the excellent book, Extreme Weather, by Chris Burt. It's no problem if you don't know where Gonzaga or Northwestern State University are, there are links for each college's home page on the forecast entry page. It's pretty easy to participate, but you must make your first forecast by midnight Wednesday (tomorrow!)

Good luck to all participants!

Jeff Masters

Tornado

Updated: 18:52 GMT le 05 janvier 2012

Permalink

A wild weather Sunday

By: JeffMasters, 16:03 GMT le 13 Mars 2006

Sunday was a wild weather day across the Midwest, with 104 reports of tornadoes sent to the Storm Prediction Center, 336 reports of hail, and 89 reports of damaging thunderstorm winds. Damage survey teams are on the ground today to determine the how many tornadoes actually touched down, and how strong they were. Several of the tornadoes were 1/2 mile in width, and may have been violent F3 storms. I'll report tomorrow on the results of these damage surveys. The number of tornadoes was no doubt less than 103, since many of the tornado reports referred to the same tornado that affected more than one county.


Figure 1. Severe weather reports from Sunday's severe weather outbreak.

The severe weather will continue today, but atmospheric conditions are not nearly as volatile. The greatest threat of severe weather will be from large hail and damaging severe thunderstorm winds, although a few scattered tornadoes may pop out late this afternoon across Ohio and adjoining states. Today should be the last day of the severe weather outbreak, as the cold front associated with the strong low pressure area responsible moves off of the East Coast Tuesday morning.

Wildfires in Texas
Grass fires in drought-parched Texas killed seven people yesterday in the Panhandle, four of them in a car crash on I-40 caused by thick smoke obscuring visibility. More than 1,000 square miles of Texas burned yesterday--an area about two-thirds the size of Rhode Island. These fires were far more extensive than the ones in January that prompted the governor to declare a drought disaster. "This is probably one of the biggest fire days in Texas history," said Warren Bielenberg, a spokesman for the Texas Forest Service, in an interview with CNN. Amarillo has had only .32" of rain so far this year, compared to 1.55" in a normal year. The outlook today is more promising, as winds are expected to be lighter and temperatures cooler. The 10-day forecast is also somewhat promising, as a very active jet stream pattern is forecast to bring the chance of a major storm system to the desert Southwest and Texas early next week. However,this could also bring another severe weather outbreak to the country.


Figure 2.Latest drought map for the U.S., showing dry conditions in the Texas Panhandle that contributed to yesterday's deadly fires.

Jeff Masters

Tornado

Updated: 18:53 GMT le 05 janvier 2012

Permalink

Rain blesses Phoenix

By: JeffMasters, 17:16 GMT le 12 Mars 2006

Rain finally blessed Phoenix, Arizona on Saturday, after a record 143 straight days without precipitation. The rains were part of a large and intense weather system that spawned tornadoes that killed two people in southern Missouri, about 80 miles south of St. Louis. The storm also brought snow to the San Francisco Bay area, creating a 28-car pile up on Highway 101 just north of the Golden Gate Bridge. The stormy weather is expected to continue today, with the potential for a large tornado outbreak over the Midwest. Violent, long-track F3 or stronger tornadoes are very possible today and tomorrow in association with this powerful weather system.

At Phoenix's Sky Harbor airport, 1.4" of rain was recorded, and other areas of the city received up to three inches. Some mountain areas received up to six inches of precipitation, much of it falling as snow. Flagstaff, Arizona, which had recorded only about three inches of snow for the entire winter, had nearly 20 inches of snow fall. Numerous road closures and hundreds of traffic accidents accompanied the storm, but not many residents are complaining. The big rains and snow will help delay the start of Arizona's fire season, which was widely feared to be the worst on record due to the long dry spell. Phoenix's normal rainfall for this the year ending March 12 is 2.0 inches, so the 1.4 inches from Saturday's storm puts them close to normal precipitation for the year. Organizers of the annual St. Patrick's Day Parade and the Chandler Ostrich Festival must have bee cursing their bad luck, though, since their events happened on a rainy, cold Saturday with 25 mph winds--after 20 straight Saturdays with near perfect weather!


Figure 1. Radar estimated precipitation for the Phoenix area for Saturday, March 12, 2006. The sharp radiating lines pointing towards the radar are due to the effect of mountains blocking the radar beam.

What is the all-time record for dry spells?
Phoenix's 143 day-long dry spell may seem like a long one, but it doesn't compare to the U.S. record of 767 days, set in Bagdad, California, from October 3, 1912, through November 8, 1914. The town, on old Route 66 in the Mojave Desert in southern California, is the setting of the popular book and movie, Bagdad Cafe. The town has been nearly abandoned since 1991. Of course, neither Bagdad nor Phoenix can hold a candle to some regions of the Atacama Desert in Chile, where rain has not been recorded in the past century.

Monday's blog: Probably on the severe weather expected for today.

Jeff Masters

Drought

Updated: 21:27 GMT le 16 août 2011

Permalink

5th warmest winter on record

By: JeffMasters, 16:17 GMT le 10 Mars 2006

The winter of 2005-2006 (December, January and February) was the 5th warmest on record in the U.S., according to the National Climatic Data Center. February temperatures were near average for the U.S., with no states much warmer or much cooler than their long-term means. February 2006 was the 45th warmest on record since 1895. However, the record warm January over most of the U.S. helped push the temperatures for the winter as a whole sharply upwards. The global numbers are not tabulated yet, but it is likely that the winter will rank in the top 15 warmest winters globally, since December was the 9th warmest December on record, and January was the 13th warmest. The very cold temperatures seen in Asia during January 2006, plus the emergence of La Ni�a, will keep the global winter from setting any records for warmth.


Figure 1. Global temperatures in January 2006 were the 13th warmest on record, and the warmest on record in the U.S. Note the cool blue dots along the Equator off the Pacific coast of Central America, indicating the presence of La Ni�a cooling of the ocean surface. It is unprecedented in the historical record for a La Ni�a of this intensity to develop so early in the year.

Precipitation for the winter of 2005-2006
Precipitation was much below average in February for much of the U.S., making this February 2006 the 9th driest on record. December-February precipitation was near normal for the U.S. as a whole, but portions of the south-central U.S. and southwest U.S. suffered acute drought conditions. However, the Southwest is poised to receive its biggest storm of the season Saturday, when a half-inch of rain is expected in Phoenix, bringing its amazing string of 143 straight days without rain to an end. Up to foot of snow is expected in the mountains near Phoenix. Not much precipitation is likely for the upcoming months, though, as the persistent La Ni�a pattern should act to keep the jet stream and major storm systems well north of the Southwest.



Figure 2. Precipitation for the winter of 2005-2006 averaged near normal for the country, with the very dry conditions in the south-central and southwest U.S. being balanced by heavy precipitation in the northwestern U.S.

Tropical outlook for March
The oceans in the Northern Hemisphere are near their yearly minima in temperature this week. In the Atlantic, only the Caribbean is above the minimum 26 C threshold for hurricane formation. Wind shear remains high over the entire Atlantic, and is forecast to remain high for at least the next ten days. I'm not anticipating any off-season tropical development in the Atlantic this March. As the sun crosses the Equator on Spring Equinox (March 20), the oceans will slowly begin to heat up again.

Hottest temperature ever recorded
OK, so this isn't meteorology, but yesterday scientists at Sandia National Laboratories announced they had produced a superheated gas with the hottest temperature ever recorded--3.6 billion degrees Fahrenheit, or 2 billion degrees Centigrade. The Sun checks in at a mere 15 million degrees Centigrade.

Jeff Masters

Climate Summaries

Updated: 22:34 GMT le 21 octobre 2011

Permalink

La Nia strengthens

By: JeffMasters, 16:20 GMT le 09 Mars 2006

La Nia continues to influence our weather, and has strengthened some in the past month, according the the latest discussion issued today by NOAA's Climate Prediction Center. They predict that La Nia will continue at least until June, and probably into October. If this prediction holds true, we are likely to see another very active hurricane season in the Atlantic, as wind shear is typically quite low over the Atlantic during La Nia conditions. Dr. Bill Gray's forecast (issued December 6) is calling for 17 tropical storms (average is 11), 9 hurricanes (average is 6), and 5 intense hurricanes (average is 2-3). It will be interesting to see if the stronger than expected La Nia conditions will cause him to raise his numbers in his forthcoming April 4 forecast for the 2006 hurricane season. The NOAA hurricane forecast will be issued in mid-May.


Figure 1. Heavy La Nia rains fell in mid-February over the Philippines, triggering a devastating mud slide that killed over 1500. Image credit: NASA's TRMM project.

La Nia has brought increased rains to portions of Ecuador, northern Peru, Hawaii (which suffered moderate flooding problems last week), and of course the Philippines, where a devastating mud slide killed over 1500 on the island of Leyte. On the flip side, La Nia has brought drought conditions to the south-central and southwestern U.S. Phoenix, Arizona has recorded its 142nd consecutive day without rain today, and Flagstaff has recorded only 2.6" of snow this winter--77 inches below normal, and 110 inches below last year's snowfall. The Snowbowl ski area near Flagstaff was unable to open this year for the first time in its history. Rain is forecast to fall over much of Arizona on Saturday, but not enough to significantly dent the drought.

Tornadoes today
My next update depends on the weather--severe weather and tornadoes are expected over much of the southern U.S. today, and we'll see what storms develop. Already this morning, tornadoes have been reported in Arkansas and Tenessee, along with damage from 70 mph thunderstorm winds and baseball-sized hail.

Jeff Masters

Updated: 18:01 GMT le 28 juin 2006

Permalink

Antarctica melting?

By: JeffMasters, 18:44 GMT le 07 Mars 2006

Melting ice in Antarctica produced global sea level rises of 0.4 mm/year between 2002 and 2005, according to a new study published March 2, 2006 in the on-line journal Science Express. The study, titled "Measurements of Time-Variable Gravity Show Mass Loss in Antarctica", by University of Colorado researchers Isabella Velicogna and John Wahr, used satellite data from two NASA satellites called the Gravity Recovery and Climate Experiment (GRACE). The satellites measured the changing pull of gravity from the two large ice sheets covering Antarctica to determine how much ice was on the continent, and how fast the ice was changing. Most of the melting discovered was from the West Antarctic Ice Sheet. This is the smaller of the two ice sheets covering Antarctica, and holds enough ice to raise global sea levels 20 feet should it completely melt. The rock on which the West Antarctic ice rests is below sea level, and the sheet could be melting on its underside due to warming ocean waters penetrating there and melting it from both below and along the edges. The study found little melting of the huge East Antarctic Ice Sheet (which would raise global sea levels 200 feet if it were to melt). This ice sheet is on rock high above sea level, so warmer ocean waters cannot affect it. Additionally, the East Antarctic Ice Sheet has average temperatures so cold that even a 5-10C increase in temperatures is not expected to seriously threaten it.

The net Antarctic melting reported comes as a surprise, since the "official" prediction from the latest 2001 report from the Intergovernmental Panel on Climate Change is that global warming should cause increased precipitation over Antarctica this century. This increased precipitation is expected to exceed Antarctica's melting enough to decrease global sea level. This decrease in sea level by 2100 is predicted to be about 3 inches (8 cm), � 4 inches (10 cm), but would be offset by increases in sea level due to thermal expansion of the seas due to warmer water temperatures, plus melting of Greenland and glaciers on other continents.

As I reported in my blog on Greenland's greenhouse, total global sea level rise in recent years has been between 1.5 and 2.9 mm/year. Thus, the .4 mm/year contribution from Antarctica found by the new study represents a significant portion of this rise. However, another study published in December 2005 in the Journal of Glaciology titled, "Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002" found a rate of melting for Antarctica five times smaller, for the earlier period 1992-2002. This research, performed by a team led by NASA scientist H. Jay Zwally, used satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2, and found a net melting of only .08 mm/year from Antarctica. Did Antarctica's melting really increase 5-fold in past three years? If so, is this a short term fluctuation, or indication of a long term trend? I'm of the opinion that's it's too soon to tell. It is extremely difficult to do mass balance studies of these huge ice sheets, since it requires finding a small change in a very large number. The same problem affects the recent estimates of Greenland's mass balance. The new study from the Journal of Glaciology also reported that between 1992 and 2002, the total mass of the Greenland Ice Sheet increased and thus Greenland caused a .03 mm/year decrease in sea level. This result is in contradiction to the two studies I quoted in my Greenland blog, by Box et al. (2004), who found that Greenland contributed to a net increase in global sea level of 1.5 mm/year, and Rignot et al. (2006), who found a .23 mm/year rise for the year 1996, increasing to .57 mm/year by 2005. I'd like to see at least three to five more years of satellite measurements before concluding that Antarctica or Greenland are undergoing significant melting. The European Space Agency is launching a satellite called CryoSat in March 2009 that should help answer these questions. If you want a more technical discussion of the issues, realclimate.org published a nice analysis last week.

Coverage in the press
It was interesting to watch the reaction of the press to the release of the new study. The New York Times titled their article, "Loss of Antarctic Ice Increases", and did a reasonable job covering some of the uncertainties. The USA Today was a bit more alarmist, headlining their article, "Study: Antarctic ice sheet in 'significant decline'". The Washington Post had a very alarmist title to their article, "Antarctic Ice Sheet Is Melting Rapidly". The facts and uncertainties involved in the making ice sheet balance measurements do not support this claim, as of now. Although any news of an increase in melting from Antarctica or Greenland is worthy of concern, I thought that in general, the media's headlines on the matter were too alarmist, given the uncertainties involved.

My next blog will be Thursday, when perhaps I'll be able to talk about Phoenix's first rain in 142 days. They've got a 20% chance of rain on Wednesday!

Jeff Masters

References
Box, J.E., D.H. Bromwich, and L-S Bai, 2004. Greenland ice sheet surface mass balance 1991-2000: Application of Polar MM5 mesoscale model and in situ data. J. Geophys. Res., 109, D16105, doi:10.1029/2003JD004451.

Rignot, E., and P. Kanagaratnam, "Changes in the Velocity Structure of the Greenland Ice Sheet" Science 311, 986-990, 17 February 2006, DOI: 10.1126/science.1121381

Climate Change

Updated: 21:19 GMT le 16 août 2011

Permalink

Hurricane humor

By: JeffMasters, 16:59 GMT le 06 Mars 2006

The great thing about attending weather conferences is that you never know what you might learn from the new people you meet. At the annual conference of the American Meteorological Society last month, I had the opportunity to interview a number of candidates for a job opening at wunderground.com, and learned something interesting about Hurricane Katrina I didn't know. (By the way, if you're a skilled C language programmer with a background in meteorology, we're looking to hire!.) The student I interviewed, Chris Smith, attended college in Daytona Beach. He said that during the week following Hurricane Katrina's devastation, beer retailers in the Daytona Beach area were stuck with a huge shipment of beer that was intended for the normally very busy Labor Day weekend period in New Orleans. With no place for the beer to go, local retailers offered steep discounts, and some enterprising college students stocked up big-time. Chris' friend Joe Funkhouser can be seen below posing on his "beer throne" of half-price Katrina beer.


Figure 1. A "beer throne" contructed out of half-price beer on sale because it couldn't make it to New Orleans in the wake of Hurricane Katrina.

National Weather Service to give hurricanes full names

The Onion, the Internet's premier humor newspaper, announced today that hurricanes will now be given a last name in addition to a first name. So, instead of plain old boring "Alberto" for the year's first storm, we'll have "Alberto Fergus." No word on what the last names of Greek storms Alpha, Beta, and so on will be. Alpha Male? Beta Max?

Jeff Masters


Humor

Updated: 23:18 GMT le 16 août 2011

Permalink

Acidifying the oceans

By: JeffMasters, 19:38 GMT le 03 Mars 2006

It is well known that CO2 in the atmosphere has risen from about 275 ppm (.0275%) to 375 ppm (.0375%) since the Industrial Revolution began in the 1800s. This extra CO2, added to the atmosphere by the burning of fossil fuels, has contributed to the observed rise in global temperatures of 0.6 degrees C via the greenhouse effect. What is less well known, and is discussed in detail in a March 2006 article in Scientific American called "The Dangers of Ocean Acidification", is that a tremendous amount of the CO2 emitted by fossil fuel burning winds up in the oceans. The oceans have absorbed 48% of all the CO2 emitted since 1800, according to a study published by Sabine et al. in 2004 in Science. Without the action of the oceans to absorb so much of our waste gases we've pumped into the atmosphere, Earth would be a seriously toasty planet right now.

The price paid
The oceans are paying a price for this service, though. When CO2 dissolves into the ocean, it creates carbonic acid--the same acid found in soda pop. The oceans have dissolved so much CO2 during the past 150 years that the acidity of the oceans' surface waters has substantially increased. The pH, which decreases as acidity increases, used to range from 8.0 to 8.3 for the oceans' surface waters before the Industrial Revolution. This has now dropped a full 0.1 units to the 7.9 to 8.2 range. Unless significant cuts in CO2 emissions are realized in the next few decades, the pH will fall another 0.3 units by the year 2100 as the oceans continue to acidify. A 2005 report by the Royal Society of the UK projects the decrease by 2100 will be 0.5 pH units, and notes that it will take more than 10,000 years for the ocean to return to its pre-1800s acidity level.

Losers
Higher acidity in the ocean creates problems for a number of organisms. Corals and other creatures that build shells out of calcium carbonate are particularly vulnerable, since they cannot form their shells if the acidity passes a critical level--their shells will dissolve. Several shell-building planktonic organisms, such as coccolithophorids, pteropods, and foraminifera, form an important basis of the food chain in the cold waters surrounding Antarctica. The effect of ocean acidification is more pronounced at colder temperatures, and it is believed that these important micro-organisms will die out or be forced to move to warmer waters in order to survive in the coming decades. What this will mean to the birds, fish, marine mammals, and humans that depend on the oceans for their livelihood is unknown. Major die-offs of many species are quite possible, which would have serious impacts for nations such as Chile, where marine-related activities provide more jobs than any other sector of the economy. The effects on the Atlantic are expected to be delayed several decades compared to the Southern Hemisphere oceans, but are still expected to be significant by the end of the century.

Corals in tropical and subtropical waters will not dissolve in the more acidic waters, but the increased acidity will cause them to grow more slowly. When this added stress is added to the already significant impacts of coral bleaching from global warming, pollution, and destruction due to dynamiting of reefs to harvest fish, the outlook for coral reefs this century is exceedingly bleak. About one-third of the world's coral reefs have already been damaged or destroyed in the past century, with another one-third at serious risk of destruction by 2030.

The effect of higher oceanic acidity and CO2 levels on higher organisms such as fish, birds, and sea mammals is largely unknown. These effects are unlikely to be beneficial to fish, though--high levels of CO2 are sometimes used by researchers to euthanize fish.

Winners
Higher dissolved CO2 in the oceans will benefit a number of species. For example, many higher plants such as sea grasses use dissolved CO2 directly to help them grow, and should prosper from higher CO2 levels in the ocean, just as many plants on land are expected to benefit from higher atmospheric CO2 levels. Some types of phytoplankton will probably benefit as well, although laboratory studies on this are not conclusive. Other species of phytoplankton will likely be unaffected. The Royal Society of the UK report concluded, "the increase of CO2 in the surface oceans expected by 2100 is unlikely to have any significant direct effect on photosynthesis or growth of most micro-organisms in the oceans."

What the future holds
Ocean life can adapt to higher acidity. One study (Spivack et al., 1993) found that pH levels in the ocean 7.5 million years ago were about 7.4, well below today's pH. The big concern with the current increase in acidity and drop of ocean pH levels is that it is being compressed into such a short period of time. Past changes in oceanic acidity have presumably occurred over tens of thousands of years, giving time for life to adapt. The current change may occur so fast that a partial collapse of the food chain in some regions may occur. One note of optimism: similar concerns were voiced when the Antarctic ozone hole opened up, exposing phytoplankton in the Southern Hemisphere oceans to a rapid and unprecedented increase in levels of damaging ultraviolet radiation. It was widely feared that this increase in UV light would destroy enough phytoplankton to trigger a collapse of the food chain in the waters off of Antarctica. This has not happened. One study (Smith et. al., 1992) found a 6-12% decrease in phytoplankton during the time the ozone hole opens up, typically about 10-12 weeks of the year. So, at least in this one case, the marine ecosystem was able to adapt to a rapid, unprecedented change and not collapse.

As is the case with many aspects of human-caused climate change, the dangers are enormous, but poorly understood. In the words of the Dr. Doney's Scientific American article, "dramatic alterations in the marine environment appear to be inevitable." The Royal Society's article cautions, "research into the impacts of high concentrations of CO2 in the oceans is in its infancy and needs to be developed rapidly." The report goes on to state, "Ocean acidification is a powerful reason, in addition to that of climate change, for reducing global CO2 emissions. Action needs to be taken now to avoid the risk of irreversible damage to the oceans. We recommend that all possible approaches be considered of prevent CO2 reaching the atmosphere. No option that can make a significant contribution should be dismissed."

Jeff Masters

References

Sabine et al., "The Oceanic Sink for Anthropogenic CO2", Science, 305, 367-371, 16 July 2004.

Smith, R., B. Prezelin, K. Baker, R. Bidigare, N. Boucher, T. Coley, D. Karentz, S. MacIntyre, H. Matlick, D. Menzies, M. Ondrusek, Z. Wan, and K. Waters, "Ozone depletion: Ultraviolet radiation and phytoplankton biology in Antarctic waters", Science, 255, 952, 1992.

Spivack, A.J., You, C., and H.J. Smith, "Foraminiferal boron isotope ratios as a proxy for surface ocean pH over the past 21 Myr", Nature, 363, 149-151, 13 May 1993, doi:10.1038/363149a0.

Climate Change

Updated: 21:19 GMT le 16 août 2011

Permalink

International Environmental Data Rescue Organization

By: JeffMasters, 18:13 GMT le 01 Mars 2006

While persusing the booths at this year's annual meeting of the American Meteorological Society, I stumbled across the International Environmental Data Rescue Organization (IEDRO), and non-profit organization dedicated to saving old climate records throughout the world. I quickly signed up the Weather Underground to be a financial supporter, and urge those of you interested to contribute to this worthwhile charity!

IEDRO works primarily in third-world countries such as Kenya, Malawi, and the Dominican Republic. They hire and train local people to scan in paper climate records using a digital camera. The data are then keyed into a computer in comma-delimited format, burned onto a CD-ROM, and sent via
courier from the local U.S. embassy directly to the U.S. The final CD-ROMs end up at the National Climatic Data Center (NCDC).

In many of the countries IEDRO works in, the old climate records are literally molding away in old cardboard boxes. These records often have decayed into non-legibility. So, IEDRO is in a race against time to save the data before they are permanently lost. With the issue of climate change quickly emerging as one of the most important scientific challenges of all time to solve, as much historical data as possible needs to be saved so that we can better see where climate change might be occurring. IEDRO also provides employment to third-world workers who typically desperately need jobs, so IEDRO's efforts have a double benefit.


Dr. Rick Crouthamel of IEDRO describes how the workers they hire digitize data, using the digital camera on the stand behind him.

My next blog will be Friday.

Jeff Masters

Climate Change

Updated: 21:19 GMT le 16 août 2011

Permalink

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Scattered Clouds
82 ° F
Nuages épars